1. Field of the Invention
This invention relates generally to surgical procedures employing a flexible catheter guide and more particularly to an apparatus for use in balloon angioplasty.
2. Prior Art
Catheters require the capability of being pushed and flexibility in order to be effectively inserted into blood vessels and maneuvered through a vascular tree. Often a hollow spring wire shaft is used as a catheter, such catheter including a movable core wire.
A balloon may be used in conjunction with various catheter constructions such that the balloon may be inflated within the vessel, thereby opening blockages found therein. However, the combination of a hollow spring wire shaft and a movable core wire of variable properties has not been used in conjunction with a balloon.
U.S. Pat. No. 4,276,874 discusses a balloon catheter including an elongated coil spring defining an inner passage, the spring being covered by silicone in the form of an extendable sheath, strain collar, and a balloon tip affixed to the strain relief collar. A portion of the elongated coil spring and sheath form a support structure which perceptibly elongates when excessive stretching force is applied to the support structure when moving the balloon through a body passage. Unfortunately, such a catheter is unsteerable and does not have variable flexibility.
Another device, disclosed in U.S. Pat. No. 4,723,936, is a coil spring guide including a deflectable tip which comprises a coil spring covered by a sheath, a core wire within the coil spring extending the length of the coil spring, and a head member. At the proximal end of the coil spring guide a mechanism is provided to enable movement of the coil spring relative to the core wire. The core wire is eccentrically fixed to the back side of the head member and adjacent a lateral side thereof, thereby causing compression of the distal and spring coils and deflection thereof in a direction laterally from the side of the head member to which the core extension is fixed upon rearward movement of the core wire. Such a standard low profile catheter with a fixed wire system additionally does not offer a combined over-the-wire system nor variable column strength.
Still another device, disclosed in U.S. Pat. No. 4,548,206, is directed to a catheter wire guide with a movable mandrel having a tapered tip which permits the flexibility of the distal tip of the wire guide to be varied. This device provides for a helically wound wire having an opening therethrough and a mandrel positioned within the opening and longitudinally movable therein relative to the helically wound wire for varying the flexibility of the distal tip of the wire guide. The device is a diagnostic or wire placement device and not a balloon catheter suitable for angioplasty.
Although the foregoing devices include some advantageous features, they are limited in that they do not combine the following desirable features: a movable core means; variable stiffness of the shaft secondary to the movable core means and therefore variable trackability and pushability; a deflection mechanism for deflecting the tip of the catheter while still allowing torque and rotation; an ultra low profile, such that the device may be used in conjunction with a standard diagnostic coronary catheter rather than a guide catheter, referred to as a PTCA guiding catheter; the capability to transform from a fixed wire system to an over-the-wire system by removal of the movable core means; and the ability to insert either fiber optic angioscopes or laser fibers through the hollow portion of the catheter.
The foregoing illustrates limitations known to exist in present devices. Thus, it is apparent that it would be advantageous to provide an alternative device directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is herein provided including features more fully disclosed hereinafter.